1. Field of the Invention
This invention relates to a method for diagnosis of components used inside a turbine generator for power supply, by which method the state of a gas inside the turbine generator is investigated to diagnose the components.
2. Description of the Prior Art
Roughly two methods have been known to diagnose components used inside a turbine generator by investigating a gas inside the turbine generator.
One of the methods is adopted in a device called "Generator-ConditionMonitor," a product of Environment-One, the United States, as shown, for example, in publication 1 (IEEE Conference Paper, 71C, p. 154 (1971)). This device is already commercially available.
The Generator-Condition-Monitor and the Ion-Chamber-Detector in common use are the same in the principle of action and the way of diagnosis.
FIG. 6 is a structural diagram of the Ion-Chamber-Detector in general use. This Ion-Chamber-Detector will be described first.
In FIG. 6, the reference numeral 7 designates a power instrument line for introduction of a gas that has filled up a turbine generator. In the publication 1, a hydrogen gas is used as this gas. The reference numeral 9 designates a device container, and the reference numeral 10 designates an a radiation source for irradiating the gas, which has been introduced into the device container 9, with .alpha. rays. The reference numerals 11 and 12 designate, respectively, an electrode for applying a voltage, and an electrode for applying a voltage of a polarity opposite to the polarity of the electrode 11. The reference numeral 13 designates an ammeter for measuring an electric current flowing between the electrode 12 and the device container 9 at zero potential. The reference numeral 8 designates an outlet for the gas.
The action of the device illustrated in FIG. 6 will be described next.
Part of the hydrogen gas filled in the turbine generator is guided to the power instrument line 7, and then introduced into the device container 9 through the opening of the power instrument line 7. The hydrogen gas introduced into the device container 9 is ionized with a rays irradiated by the a radiation source 10. Then, the gas is guided by an electric field formed between the electrode 11 and the electrode 12, and flowed into the turbine generator again past the gas outlet 8.
If the hydrogen gas inside the turbine generator is free from organic substances, the ionized hydrogen molecules are light and easily movable. Thus, these molecules move easily under the electric field between the electrodes 11 and 12, reaching the electrode 12. As a result, a certain electric current is detected by the ammeter 13. If the hydrogen gas inside the turbine generator contains organic substances, on the other hand, the ionized organic substances are heavy and minimally move. This results in a decreased proportion of the hydrogen gas reaching the electrode 12. Consequently, a smaller electric current than with the hydrogen gas containing no organic substances is detected by the ammeter 13.
In other words, when the gas in the turbine generator is free from organic substances, a relatively large current flows through the ammeter 13. Whereas when the gas in the turbine generator contains organic substances, only a small current flows through the ammeter 13. Furthermore, the decrease in the current differs according to the amount of the organic substances entering the device container 9. The larger the amount of the organic substances, the greater the decrease in the current becomes, so that the value of the current becomes closer to zero amperes.
A conventional method of diagnosis using the Ion-Chamber-Detector shown in FIG. 6 will be described.
When the turbine generator is assumed to be working normally, the value of an electric current is detected by the ammeter 13. This value is recorded as the level of current during normal operation. Constantly or where necessary, the gas is introduced through the gas introduction line 7 into the device container 9 to detect an electric current. If the value of this current is lower than the previously recorded normal level, the total amount of the organic substances in the gas inside the turbine generator is presumed to have increased from the level during normal operation. This increase in the amount of the organic substances in the gas means that components composed of organic materials inside the turbine generator may be thermally decomposing. Thus, monitoring of a decrease in the current detected, namely, the total amount of the organic substances in the gas, makes it possible to diagnose whether the components inside the turbine generator are overheating or not.
In short, one of the conventional diagnostic methods has been to monitor the total amount of the organic substances in the gas inside the turbine generator, and estimate whether or not overheating is occurring in the components composed of organic materials and used in the turbine generator.
The second conventional method is described in publication 2 (IEEE Trans., PAS-100, p. 4983 (1981)) and publication 3 (IEEE Trans., PAS-95, p. 879 (1976)). This method comprises passing a gas in a turbine generator through a filter or an adsorbent, and then analyzing organic substances trapped in the filter or adsorbent by gas chromatography to identify the organic substances in the gas inside the turbine generator.
In the publication 2, moreover, a substance which will be released upon overheating of a component inside a turbine generator is incorporated into the component beforehand. Then, the substance in the gas detected by gas chromatography in the above manner is checked to see if it is identical with the incorporated substance. It is diagnosed thereby whether the component inside the turbine generator is overheating or not.
The publication 3 describes that the gas chromatographic identification of the organic substances in the turbine generator can result in a diagnosis of whether overheating is occurring or not. However, it does not describe a concrete method for diagnosis, nor the relation between overheating and the organic substances.
In summary, one of the conventional methods for diagnosis is to monitor the total amount of organic substances in the gas inside the turbine generator, thereby estimating the presence or absence of overheating in the organic materials used inside the turbine generator. The other method is to collect organic substances in the gas inside the turbine generator and identify them by means of a gas chromatograph, thereby estimating the presence or absence of overheating in the organic materials in the components used inside the turbine generator.
One of the above earlier methods for diagnosis of components inside the turbine generator detects the total amount of organic substances in the gas inside the turbine generator. Thus, it cannot discriminate among numerous organic substances present in the gas. There may be a case in which an organic substance unrelated to the materials for the components, such as a lubricating oil, is present in the gas, and no abnormality occurs in the turbine generator. That method sometimes diagnosed this case as a case of overheating. Even when diagnosing overheating correctly, the method was unable to specify which component was suffering overheating.
According to the other diagnostic method, it is possible to distinguish among organic substances in the gas inside the turbine generator by gas chromatography. However, information is lacking about which substance is suitable for use as a standard of judgment for diagnosis of the material, or what concrete procedure or method is suitable for diagnosis. This has posed extreme difficulty in making a precise diagnosis.
Besides, the above conventional method of diagnosis incorporates, beforehand, a substance, which can be easily released upon heating, into the component inside the turbine generator, thereby permitting a diagnosis of whether overheating is occurring or not, and the identification of the overheated component. With this method, however, it has been essential to incorporate, in advance, a special material into the component when producing the turbine generator. This has required more than ordinary labor and cost for the production of the component. This method has been directed only at a turbine generator containing a special substance in the components. With a previously produced turbine generator containing no special substance in the components, no effects were obtained at all. Actually, most of the turbine generators previously manufactured are free from such a special substance. Hence, this method for diagnosis is effective in an extremely limited number of the turbine generators now in operation.
Furthermore, all the above-described diagnostic methods that have been used in the diagnosis of turbine generators have merely detected whether overheating of the components is present or absent. They have been unable to diagnose heat deterioration at nearly the operating temperature of the generator that does not lead to overheating, or deterioration due to discharge, corrosion or friction.